Endocrine tissue associated with the pancreatic ductal system: a light and electron microscopic study of the adult rat pancreas with special reference to a new endocrine arrangement

BACKGROUND: A substantial part of the endocrine pancreas has been previously described as being located either close to the excretory ducts as small clusters of endocrine cells and as Islets of Langerhans, or associated with the ducts as single endocrine cells scattered through the ductal epithelium. METHODS: Four Wistar white adult rats were sacrificed and perfused via the thoracic aorta with 2.5% glutaraldehyde. After the usual treatment for the transmission electron microscopy, pieces of pancreas were sectioned consecutively for light microscopy. Consecutive ultrathin sections were performed in the most interesting cases. RESULTS: The observations previously reported were confirmed. In addition, a new endocrine arrangement was detected and described as buds of endocrine cells (mainly B-cells) protruding from the ductal epithelium into the surrounding tissue. CONCLUSIONS: The authors propose to explain the endocrine buds as components of the gastro-entero-pancreatic system or as a stage of an endocrine pancreatic "neo-histogenesis" occurring in the adult rat pancreas.